Good analogy!

I'd say on a desktop computer up to 60°C on the CPU is acceptable, beyond 70-80 is probably an indication of something slightly suspicious. I have personally never had heating problems on my 24" iMac (C2D 2007).
Regarding the screen size, am I the only person who doesn't hope to see an increase to 30" on iMacs?? I have a 24", as mentioned earlier, and I am perfectly content with it. I have done some design work on a 27" iMac and I have to say I find it a bit too large to work with. Sure it's cool to watch a movie or football game on a larger screen, but it's a bit tiring to the eye and neck to work intensively in front of one of those. I'd personally welcome the option of getting a 24" option again, for instance 24" and 30" as options. Also glossy screen is pretty annoying sometimes.
It's pretty annoying that the "best" hardware is usually available only in the largest machines (desktop and laptop alike), but I guess they have to justify the price tag.
Otherwise I hope for a re-design as well, not because the current design is faulty in any way, but because the current design is getting old and I am hoping for some innovative changes. Oh and...